“There’s the old saw that everyone knows smoking is bad for you,” said Dr. Tim McAfee of the Centers for Disease Control and Prevention. “But this paints a much more dramatic picture of the horror of smoking. These are real people that are getting 10 years of life expectancy hacked off — and that’s just on average.”

The findings were part of research, published on Wednesday in The New England Journal of Medicine, that looked at government data on more than 200,000 Americans who were followed starting in 1997. Similar studies that were done in the 1980s and the decades prior had allowed scientists to predict the impact of smoking on mortality. But since then many population trends have changed, and it was unclear whether smokers today fared differently from smokers decades ago.

Since the 1960s, the prevalence of smoking over all has declined, falling from about 40 percent to 20 percent. Today more than half of people that ever smoked have quit, allowing researchers to compare the effects of stopping at various ages.

Modern cigarettes contain less tar and medical advances have cut the rates of death from vascular disease drastically. But have smokers benefited from these advances?

Women in the 1960s, ’70s and ’80s had lower rates of mortality from smoking than men. But it was largely unknown whether this was a biological difference or merely a matter of different habits: earlier generations of women smoked fewer cigarettes and tended to take up smoking at a later age than men.

Now that smoking habits among women today are similar to those of men, would mortality rates be the same as well?

“There was a big gap in our knowledge,” said Dr. McAfee, an author of the study and the director of the C.D.C.’s Office on Smoking and Public Health.

The new research showed that in fact women are no more protected from the consequences of smoking than men. The female smokers in the study represented the first generation of American women that generally began smoking early in life and continued the habit for decades, and the impact on life span was clear. The risk of death from smoking for these women was 50 percent higher than the risk reported for women in similar studies carried out in the 1980s.

“This sort of puts the nail in the coffin around the idea that women might somehow be different or that they suffer fewer effects of smoking,” Dr. McAfee said.

It also showed that differences between smokers and the population in general are becoming more and more stark. Over the last 20 years, advances in medicine and public health have improved life expectancy for the general public, but smokers have not benefited in the same way.

“If anything, this is accentuating the difference between being a smoker and a nonsmoker,” Dr. McAfee said.

The researchers had information about the participants’ smoking histories and other details about their health and backgrounds, including diet, alcohol consumption, education levels and weight and body fat. Using records from the National Death Index, they calculated their mortality rates over time.

People who had smoked fewer than 100 cigarettes in their lifetimes were not classified as smokers. Those who had smoked at least 100 cigarettes but had not had one within five years of the time the data was collected were classified as former smokers.

Not surprisingly, the study showed that the earlier a person quit smoking, the greater the impact. People who quit between 25 and 34 years of age gained about 10 years of life compared to those who continued to smoke. But there were benefits at many ages. People who quit between 35 and 44 gained about nine years, and those who stopped between 45 and 59 gained about four to six years of life expectancy.

From a public health perspective, those numbers are striking, particularly when juxtaposed with preventive measures like blood pressure screenings, colorectal screenings and mammography, the effects of which on life expectancy are more often viewed in terms of days or months, Dr. McAfee said.

“These things are very important, but the size of the benefit pales in comparison to what you can get from stopping smoking,” he said. “The notion that you could add 10 years to your life by something as straightforward as quitting smoking is just mind boggling.”

Last modified: January 24, 2013
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